Metal Carbonyls-Structure, Properties, Organometallic compounds, Applications, FAQs

What are Metal Carbonyls ?

Structure of Metal Carbonyls

Bonding in Metal Carbonyl is achieved by the formation of both σ and π bonds. Thus the formation of metal carbonyl consists of two steps:

  • Formation of σ bond: This bond is formed due to the donation of electrons by the carbonyl molecules in the vacant orbitals of the metal. This results in the overlap of the non-bonding orbitals of the Carbon atom with the vacant orbitals of the metal atom.
Carbonyls are coordination complexes that are formed by transition metals and the carbonyl ligand i.e. carbon-monoxide ligand. These are also termed homoleptic carbonyls. These complexes have a simple and well-defined structure which is generally tetrahedral and octahedral in nature. Nomenclature of Coordination Compounds is done using specific rules.

Formation of σ bond

  • Formation of π bond due to back bonding: This bond is formed due to the donation of pair of electrons from the filled d-orbitals of the metal atom to the vacant π (π antibonding) orbitals of the Carbonyl ligand or molecule. As electrons from the metal fill the π-antibonding orbital of CO, they then weaken the carbon-oxygen bond compared with the free carbon monoxide, while the metal-carbon bond is strengthened. This bond is formed due to back bonding as the metal atom donates a pair of electrons from its filled d-orbitals to the empty π– antibonding orbitals of the CO ligand. This type of bonding is also known as synergic bonding.
Carbonyls are coordination complexes that are formed by transition metals and the carbonyl ligand i.e. carbon-monoxide ligand. These are also termed homoleptic carbonyls. These complexes have a simple and well-defined structure which is generally tetrahedral and octahedral in nature. Nomenclature of Coordination Compounds is done using specific rules.

Formation of π bond

Bonding in Metal Carbonyls

The carbon monoxide ligand is a unique ligand which is different from other ligands. The bond between transition metals and metal carbonyls is achieved by “synergistic π star back-bonding.” The bonding is partially similar to the triple bond. The carbonyl (CO) ligand is unsaturated, i.e. it not only donates electrons to form σ– bond but also accepts electrons in its π orbital from dπ metal orbitals. Thus the CO ligand behaves as an acidic ligand.

Properties of Metal Carbligandonyls

The important properties of metal carbonyls are discussed below in the article:

  • Metal carbonyls exist as solids at standard temperature and pressure i.e. at room temperature and standard atmospheric pressure (STP).
  • They are toxic in nature and can be fatal if inhaled as the carbonyl ion in the metal carbonyl binds with the haemoglobin in the blood to form carboxyhaemoglobin which hinders the oxygen binding capacity of haemoglobin in the blood cells.
  • They are volatile in nature as they have low melting points.
  • They are soluble in both polar and non-polar solvents.
  • On heating, they decompose to the respective metal and carbon monoxide.
  • Both metal and Carbonyl ions are responsible for the reactivity of the metal carbonyls.
  • They are carcinogenic in nature.

Types of Metal Carbonyls

Metal carbonyls can be classified into various types:

Based on Types of Ligands

  • Homoleptic Metal Carbonyls: In homoleptic carbonyls, only one type of ligands i.e. CO ligands are present. They are represented using the general formula Mx​(CO)y
  • Heteroleptic Metal Carbonyls: Heteroleptic carbonyls contain CO ligands along with other types of ligands such as -Cl, -Br, -I, etc. They are represented using the MxLm​(CO)y general formula.

Based on The Number of Metal Centres Involved in Forming The Complex

  • Mononuclear metal carbonyl: These metal carbonyls have only one metal centre. The general formula of mononuclear metal carbonyls is M(CO)x
  • Polynuclear metal carbonyl: These metal carbonyls have two or more metal centres. The general formula of mononuclear metal carbonyls is MxNy​(CO)z

Uses(Applications) of Metal Carbonyls

  • Nickel carbonyl is used to produce pure Nickel using the Mond process.
  • Iron carbonyls are used to prepare dietary supplements.
  • They are used in organic synthesis and as catalysts.
  • They are being used as drugs to release CO.
  • They are also used to create aldehydes.

Metal Carbonyls Organometallics

These compounds have at least one metal-carbon bond and the carbon atom is a part of an organic group. Some common examples of organometallics are Grignard Reagent – RMgX, Gilman Reagent – R2CuLi, Dimethylmagnesium – Me2Mg, Triethylborane – Et3B, Ferrocene, Cobaltocene. These compounds are very important in the field of chemistry.

Properties of Organometallics

The properties of Organometallic compounds are:

  • Most of them exist in a solid state.
  • Some of them may be present in both liquid and gaseous states.
  • Organometallics formed by electropositive elements such as lithium, aluminium can be flammable in nature.
  • They are very toxic and volatile in nature.
  • They are not soluble in water but in ethers.
  • They are very reactive in nature.
  • They have high electronegativity.

Uses of Organometallics

The uses of Organometallic compounds are:

  • They are used as reagents in organic reactions.
  • They are used in the treatment of syphilis.
  • Grignard reagent which is an organometallic is widely used in organic chemistry.
  • Cis-Plastin is used as an anti-cancer drug.
  • They are used as additives.

FAQs on Metal Carbonyls

Question 1: Define metal carbonyls with examples.

Answer:

Metal carbonyls are coordination complexes that are formed by transition metals and the carbonyl ligand i.e. carbon-monoxide ligand. Ni(CO)4 is an example of metal carbonyl.

Question 2: Give any 2 properties of metal carbonyls.

Answer:

  • They are toxic in nature and can be fatal if inhaled as the carbonyl ion in the metal carbonyl binds with the haemoglobin in the blood to form carboxyhaemoglobin which hinders the oxygen binding capacity of haemoglobin in the blood cells.
  • They are volatile in nature as they have low melting points.

Question 3: List any 3 uses of metal carbonyls R2CuLi

Answer:

Uses of metal carbonyls are:

  • Nickel carbonyl is used to produce pure Nickel using the Mond process.
  • They are also used to create aldehydes.
  • Iron carbonyls are used to prepare dietary supplements.

Question 4: What are the stages in the formation of metal carbonyls?

Answer:

The stages in the formation of metal carbonyls are:

  • Formation of a sigma bond
  • Formation of pi bond through back bonding

Question 5: What are organometallics?

Answer:

Those compounds that have at least one metal-carbon bond and the carbon atom is a part of an organic group is termed organometallics. Some common examples of organometallics are Grignard Reagent – RMgX, Gilman Reagent -R2CuLi

Er. Neeraj K.Anand is a freelance mentor and writer who specializes in Engineering & Science subjects. Neeraj Anand received a B.Tech degree in Electronics and Communication Engineering from N.I.T Warangal & M.Tech Post Graduation from IETE, New Delhi. He has over 30 years of teaching experience and serves as the Head of Department of ANAND CLASSES. He concentrated all his energy and experiences in academics and subsequently grew up as one of the best mentors in the country for students aspiring for success in competitive examinations. In parallel, he started a Technical Publication "ANAND TECHNICAL PUBLISHERS" in 2002 and Educational Newspaper "NATIONAL EDUCATION NEWS" in 2014 at Jalandhar. Now he is a Director of leading publication "ANAND TECHNICAL PUBLISHERS", "ANAND CLASSES" and "NATIONAL EDUCATION NEWS". He has published more than hundred books in the field of Physics, Mathematics, Computers and Information Technology. Besides this he has written many books to help students prepare for IIT-JEE and AIPMT entrance exams. He is an executive member of the IEEE (Institute of Electrical & Electronics Engineers. USA) and honorary member of many Indian scientific societies such as Institution of Electronics & Telecommunication Engineers, Aeronautical Society of India, Bioinformatics Institute of India, Institution of Engineers. He has got award from American Biographical Institute Board of International Research in the year 2005.

CBSE Class 12 Chemistry Syllabus Download PDF

Below is the CBSE Class 12 Syllabus along with the marking scheme and time duration of the Chemistry exam.

S.NoTitleNo. of PeriodsMarks
1Solutions107
2Electrochemistry129
3Chemical Kinetics107
4d -and f -Block Elements127
5Coordination Compounds127
6Haloalkanes and Haloarenes106
7Alcohols, Phenols and Ethers106
8Aldehydes, Ketones and Carboxylic Acids108
9Amines106
10Biomolecules127
Total70

CBSE Class 12 Chemistry Practical Syllabus along with Marking Scheme

The following is a breakdown of the marks for practical, project work, class records, and viva. The total number of marks for all parts is 15. The marks for both terms are provided in the table below.

Evaluation Scheme for ExaminationMarks
Volumetric Analysis08
Salt Analysis08
Content-Based Experiment06
Project Work and Viva04
Class record and Viva04
Total30

CBSE Class 12 Chemistry Syllabus (Chapter-wise)

Unit -1: Solutions

  • Raoult's law.
  • Colligative properties - relative lowering of vapour pressure, elevation of boiling point, depression of freezing point, osmotic pressure, determination of molecular masses using colligative properties, abnormal molecular mass.
  • Solutions, Types of solutions, expression of concentration of solutions of solids in liquids, solubility of gases in liquids, solid solutions.
  • Van't Hoff factor.

Unit -2: Electrochemistry

  • Redox reactions, EMF of a cell, standard electrode potential
  • Nernst equation and its application to chemical cells
  • Relation between Gibbs energy change and EMF of a cell
  • Kohlrausch's Law
  • Electrolysis and law of electrolysis (elementary idea)
  • Dry cell-electrolytic cells and Galvanic cells
  • Conductance in electrolytic solutions, specific and molar conductivity, variations of conductivity with concentration.
  • Lead accumulator
  • Fuel cells

Unit -3: Chemical Kinetics

  • Rate of a reaction (Average and instantaneous)
  • Rate law and specific rate constant
  • Integrated rate equations and half-life (only for zerfirst-order order reactions)
  • Concept of collision theory (elementary idea, no mathematical treatment)
  • Factors affecting rate of reaction: concentration, temperature, catalyst;
  • Order and molecularity of a reaction
  • Activation energy
  • Arrhenius equation

Unit -4: d and f Block Elements  

  • Lanthanoids- Electronic configuration, oxidation states, chemical reactivity and lanthanoid contraction and its consequences.
  • Actinoids- Electronic configuration, oxidation states and comparison with lanthanoids.
  • General introduction, electronic configuration, occurrence and characteristics of transition metals, general trends in properties of the first-row transition metals – metallic character, ionization enthalpy, oxidation states, ionic radii, color, catalytic property, magnetic properties, interstitial compounds, alloy formation, preparation and properties of K2Cr2O7 and KMnO4.

Unit -5: Coordination Compounds  

  • Coordination compounds - Introduction, ligands, coordination number, color, magnetic properties and shapes
  • The importance of coordination compounds (in qualitative analysis, extraction of metals and biological system).
  • IUPAC nomenclature of mononuclear coordination compounds.
  • Bonding
  • Werner's theory, VBT, and CFT; structure and stereoisomerism

Unit -6: Haloalkanes and Haloarenes  

  • Haloarenes: Nature of C–X bond, substitution reactions (Directive influence of halogen in monosubstituted compounds only). Uses and environmental effects of - dichloromethane, trichloro methane, tetrachloromethane, iodoform, freons, DDT.
  • Haloalkanes: Nomenclature, nature of C–X bond, physical and chemical properties, optical rotation mechanism of substitution reactions.

Unit -7: Alcohols, Phenols and Ethers   

  • Phenols: Nomenclature, methods of preparation, physical and chemical properties, acidic nature of phenol, electrophilic substitution reactions, uses of phenols.
  • Ethers: Nomenclature, methods of preparation, physical and chemical properties, uses.
  • Alcohols: Nomenclature, methods of preparation, physical and chemical properties (of primary alcohols only), identification of primary, secondary and tertiary alcohols, mechanism of dehydration, and uses with special reference to methanol and ethanol.

Unit -8: Aldehydes, Ketones and Carboxylic Acids   

  • Carboxylic Acids: Nomenclature, acidic nature, methods of preparation, physical and chemical properties; uses.
  • Aldehydes and Ketones: Nomenclature, nature of carbonyl group, methods of preparation, physical and chemical properties, mechanism of nucleophilic addition, the reactivity of alpha hydrogen in aldehydes, uses.

Unit -9: Amines    

  • Diazonium salts: Preparation, chemical reactions and importance in synthetic organic chemistry.
  • Amines: Nomenclature, classification, structure, methods of preparation, physical and chemical properties, uses, and identification of primary, secondary and tertiary amines.

Unit -10: Biomolecules     

  • Proteins -Elementary idea of - amino acids, peptide bond, polypeptides, proteins, structure of proteins - primary, secondary, tertiary structure and quaternary structures (qualitative idea only), denaturation of proteins; enzymes. Hormones - Elementary idea excluding structure.
  • Vitamins - Classification and functions.
  • Carbohydrates - Classification (aldoses and ketoses), monosaccharides (glucose and fructose), D-L configuration oligosaccharides (sucrose, lactose, maltose), polysaccharides (starch, cellulose, glycogen); Importance of carbohydrates.
  • Nucleic Acids: DNA and RNA.

The syllabus is divided into three parts: Part A, Part B, and Part C. Part A consist of Basic Concepts of Chemistry, which covers topics such as atomic structure, chemical bonding, states of matter, and thermochemistry. Part B consists of Topics in Physical Chemistry, which includes topics such as chemical kinetics, equilibrium, and electrochemistry. Part C consists of Topics in Organic Chemistry, which covers topics such as alkanes, alkenes, alkynes, and aromatic compounds.

Basic Concepts of Chemistry:

  • Atomic structure: This section covers the fundamental concepts of atomic structure, including the electronic configuration of atoms, the Bohr model of the atom, and the wave nature of matter.
  • Chemical bonding: This section covers the different types of chemical bonds, including ionic, covalent, and metallic bonds, as well as the concept of hybridization.
  • States of the matter: This section covers the three states of matter - solid, liquid, and gas - and the factors that influence their properties.
  • Thermochemistry: This section covers the principles of thermochemistry, including the laws of thermodynamics and the concept of enthalpy.

Chapters in Physical Chemistry:

  • Chemical kinetics: This section covers the study of the rate of chemical reactions and the factors that influence it, including the concentration of reactants, temperature, and the presence of catalysts.
  • Equilibrium: This section covers the principles of chemical equilibrium, including the concept of Le Chatelier's principle and the equilibrium constant.
  • Electrochemistry: This section covers the principles of electrochemistry, including the concept of half-cell reactions, galvanic cells, and electrolysis.

Chapters in Organic Chemistry:

  • Alkanes: This section covers the properties and reactions of alkanes, including their structure, isomerism, and combustion.
  • Alkenes: This section covers the properties and reactions of alkenes, including their structure, isomerism, and addition reactions.
  • Alkynes: This section covers the properties and reactions of alkynes, including their structure, isomerism, and addition reactions.
  • Aromatic compounds: This section covers the properties and reactions of aromatic compounds, including their structure, isomerism, and electrophilic substitution reactions.

In addition to the topics covered in the syllabus, the CBSE Class 12 Chemistry exam also tests students on their analytical and problem-solving skills, as well as their ability to apply the concepts learned in the classroom to real-world situations.

Students can also check out the Tips for the Class 12 Chemistry Exam. They can easily access the Class 12 study material in one place by visiting the CBSE Class 12 page at ANAND CLASSES (A School Of Competitions). Moreover, to get interactive lessons and study videos, download the ANAND CLASSES (A School Of Competitions) App.

Frequently Asked Questions on CBSE Class 12 Chemistry Syllabus

Q1

How many chapters are there in the CBSE Class 12 Chemistry as per the syllabus?

There are 10 chapters in the CBSE Class 12 Chemistry as per Syllabus. Students can learn all these chapters efficiently using the study materials provided at ANAND CLASSES (A School Of Competitions).

Q2

What is the marking scheme for CBSE Class 12 Chemistry practical exam according to the syllabus?

The marking scheme for CBSE Class 12 Chemistry practical exam, according to the syllabus, is 8 marks for volumetric analysis, 8 marks for salt analysis, 6 marks for the content-based experiment, 4 marks for the project and viva and 4 marks for class record and viva.

Q3

Which is the scoring chapter in Chemistry as per CBSE Class 12 syllabus?

The chapter Electrochemistry in Chemistry is the scoring chapter as per CBSE Class 12 syllabus.